Auxiliary Winding Input Voltage Sensing for Boost PFC Isolated Supplies
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Solution Overview
Problem
Existing input voltage sensing methods for isolated power supplies, such as attenuation networks and transformer-based systems, face inefficiencies and cost issues, particularly in providing accurate and robust voltage sensing for boost power factor correction in LED drivers.
Innovation Solution
A linear isolated power supply circuit with a boost converter and an auxiliary winding, coupled to a voltage sensing circuit that includes resistors, capacitors, and low pass filters, allowing for direct measurement of input voltage at an isolated secondary side, enabling peak or minimum detection and calculation of input power and efficiency without synchronization requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an attenuation network is used for voltage sensing, then the sensing circuit can be implemented, but the system efficiency decreases due to significant power consumption
Solution Approach 1:
The patent extracts the voltage sensing function from the primary power path by using the auxiliary winding of the boost converter. The sensing circuit is implemented on the isolated secondary side, extracting only the necessary voltage information through magnetic coupling rather than directly loading the primary side, thereby eliminating significant power consumption while maintaining sensing capability.
2Measurement precision
If a transformer connected to power mains is used, then voltage sensing can be achieved, but the device size and cost increase due to large magnetizing inductance requirements
Solution Approach 1:
The auxiliary winding of the boost converter is designed to serve dual purposes: providing power for the control circuitry and enabling input voltage sensing. By making the auxiliary winding multi-functional, the patent eliminates the need for a separate sensing transformer, thereby reducing overall device size and cost while maintaining accurate voltage sensing capability.
3Measurement precision
If a flyback topology sense circuit is used, then voltage sensing can be implemented, but the system reliability decreases due to indirect measurement and synchronization requirements
Solution Approach 1:
The patent uses the auxiliary winding as an intermediary element that magnetically couples the primary and secondary sides. This intermediary provides a direct and robust measurement path for input voltage sensing on the isolated secondary side, eliminating the need for indirect measurements and complex synchronization logic, thereby improving system reliability and robustness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides efficient and cost-effective input voltage sensing for LED drivers, allowing for accurate detection during startup and steady-state operations, even when the boost converter enters burst mode, with minimal additional components and reduced complexity.
Implementation Method 1
The auxiliary side winding may be configured to be magnetically coupled to the boost inductor winding
Implementation Method 2
the voltage sensing circuit configured to measure an input voltage at an isolated circuit associated with the auxiliary winding
Implementation Method 3
a low pass filter coupled to the cathode of the rectifying diode
Data Source
AI summary
A system for a linear isolated power supply circuit may include a boost converter having a boost inductor winding and an auxiliary side winding, the auxiliary side winding configured to be magnetically coupled to the boost inductor winding. The linear isolated power supply circuit includes a voltage sensing circuit coupled to the auxiliary side winding, the voltage sensing circuit configured to measure an input voltage at an isolated circuit associated with the auxiliary winding. The linear isolated power supply circuit includes a processor configured to receive the measured input voltage from the voltage sensing circuit and to cause at least one operation to be performed by the processor based at least in part upon the measured input voltage. Methods and apparatuses corresponding to the system are provided.